As for joining an FC, when I first started, I was approached to join a brand-new one, but I declined because I enjoy playing by myself (yes...even in an MMO). I know FCs can help with anything, but personally I didn't feel the need for any assistance until I was well past level fifty. I had stayed in contact with my friends and joined their FC then

So really it's up to you, do you want help doing all of the early story quests and dungeons? For me, the randomization of the Duty Finder was enough. Or do you want more social interaction and a community to do it with? Then I suggest looking for a good FC to join.